1. Field of the invention
This invention relates to an apparatus for erasing a plate cylinder of an offset printing press, more particularly to an apparatus which has a pair of driving units for moving an erasing member of the apparatus toward the plate cylinder to erase a printing plate of the plate cylinder.
2. Description of the Related Art
This invention is an improvement of a conventional apparatus for erasing a plate cylinder (B) of an offset printing press, as shown in FIG. 1. The offset printing press further includes an inking roller (D) and a moistening roller (C) which are mounted therewithin adjacent to the plate cylinder (B) and which are spaced apart from each other at a predetermined distance. The plate cylinder (B) carries a printing plate.
The conventional apparatus, as shown in FIGS. 1 and 2, includes an elongated guide plate (X) which is mounted to the offset printing press apart from the plate cylinder (B) and which extends in an axial direction of the plate cylinder (B) (see FIG. 1), a mounting unit (Q) which is mounted slidably on the elongated guide plate (X), and an elongated erasing member (Q1) which is mounted to the mounting unit (Q) and which extends from the mounting unit (Q) through the space between the inking and moistening rollers (D, C) to a position near the plate cylinder (B) in order to erase impurities on the printing plate of the plate cylinder (B) when the erasing member (Q1) is depressed manually against the printing plate of the plate cylinder (B). The operating steps of the conventional apparatus are follows:
Initially, a sensor (not shown) of the conventional apparatus, which is mounted on the offset printing press, detects the presence of impurities on the printing plate of the plate cylinder (B).
Then, the mounting unit (Q) of the conventional apparatus is moved manually along the guide plate (X) to align the erasing member (Q1) with the detected impurities and in accordance with scale members (Y) (see FIG. 2) which are formed on the outer surface of the offset printing press above the guide plate (X).
Finally, when the mounting unit (Q) is moved to a desired position, the erasing member (Q1) is depressed manually against the printing plate of the plate cylinder (B) so as to erase the impurities on the printing plate.
From the above described operating steps of the conventional apparatus for erasing the plate cylinder (B) of the offset printing press, we can easily discover several drawbacks. For example, the complicated operating steps involved may affect the working efficiency of the offset printing press. Next, it is quite dangerous for an operator to depress manually the erasing member (Q1) of the conventional apparatus against the printing plate of the plate cylinder (B) when the offset printing press is being actuated. In addition, the erasing member (Q1) of the conventional apparatus, when depressed manually against the printing plate of the plate cylinder (B), may result in damage to the printing plate of the plate cylinder (B) due to the application of excess depressive forces by the erasing member (Q1) on the printing plate.